1. Field of the Invention
The present invention relates to a communication system for transmitting multicast data to a plurality of mobile stations joining in a multicast group, a communication method and a mobile station suitably used for the same.
2. Description of the Related Art
Conventionally, a communication system performing broadcast communication whereby a base station transmits common information to all mobile stations in a radio area covered by the base station has been known.
A communication system performing multicast communication whereby a base station transmits common information to mobile stations joining in (belonging to) a predetermined multicast group has been known.
A communication system for transmitting multicast data using a hierarchical structure has been known.
A communication system for collecting reception capability values of the mobile stations joining in the same multicast group, and deciding the hierarchical structure of the multicast data by focusing on mobile stations having a specific reception capability (ability).
However, in the conventional communication system, when mobile stations having various reception capabilities are joining in the same multicast group, and when the hierarchical structure of the multicast data is decided by focusing on the mobile stations having a specific reception capability, the hierarchical structure of the multicast data must be decided by focusing on the mobile station having the lowest level of reception capability, so that all the mobile stations joining in the multicast group can receive the multicast data. Therefore, there has been a problem in that the reception capabilities of the mobile stations are not utilized effectively.
In addition, in the conventional communication system, there has been a problem in that even a mobile station not possessing a minimum required level of reception capability transmits a transmission request for multicast data, generating an unnecessary control load.